Biden is the nominee for the same reason he was VP: hes the relatively safe and controllable party apparat who will be paired with the (likely) gal the far Left (which is the DNC) really wants. But instead of being the lesser of evils to balance a ticket hell be the electable evil (given a good VP) to get the overt evil into office once hes deposed or dead.
The Left is using him just as it did before.
Biden is a very flawed candidate.
He has a lengthy record of decisions in his 5 decades that are antithetical to the progressives.
He has a big corruption problem with his son and family in Ukraine, China, Iraq, with Amtrak, and elsewhere.
He has a sexual assault allegation that is far more credible than the Kavanaugh witchhunt and a history of creepy behavior with women and children.
He is exhibiting signs of a lack of mental acuity with bizarre outburst, fabricated stories, and failure to remember the names of many people to include Obama.
He has a documented record of being wrong on big issues.
He has never been a good candidate failing to even achieve 10% support among the party base in his prior runs for President.
He is NOT a good candidate.